Method of producing keto acid esters



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Patented Mar. 31, 1931 UNITED STATES PATENT v OFFICE PAUL HALBIG, FELIX KAUFLER, AND rn'rnu. scnmrz, or MUNICH, GERMAN AS- smnons TO DR. ALEXANDER wncxnn GESELLSGHAFT FUR mnxrnoonnmscnn mnus'rmn e. M. B. 11., or MUNICH, BAVARIA, GERMANY a METHOD OF PRODUCING KE'IO ACID ESTEBS No Drawing. Application filed. August 1, 1928, Serial No. 296,861; and in Czechoslovakia April 26, 1928. i

It is usually assumed that the alkyl esters of the same acid show in general similar chemical characteristics. Thus in condensations in which an alkyl radical splits off, it should be immaterial whether the acid is esteritied with a methyl-, ethyl-, butyl-, or amylalcohol group. Therefore nearly all ester condensations have been effected by means of the ethylor methylesters, since the corresponding alcohols can be obtained easily and cheaply.

In ester condensations by means of metallic sodium the effect of a change in the alkyl radical (or alcohol) is small. The action of metallic sodium on butyl acetate causes, e. g. a yield of 36% while that of sodium on ethylacetate according to the known reactions causes a yield of 39 0 of the theoretical. These ratios are unexpectedly changed when the esters are condensed by means of metal alcoholates, particularly alkali metal alcoholates, such as sodium alcoholate.

For example according to this invention, the action of sodiumbutylate on butylacetate yields surprisingly about 80% or more based 011 the sodium, used in the form of sodium butylate. The invention therefore comprises the production of keto acid esters of butyl or higher alcohols by treatment of the carboxylic acid esters with a metal alcoholate, preferably of the alkali metal group.

The substitution of metallic sodium by the metal alcoholate not only efiects an essential improvement in yield in the case of butylacetate, but a number of further advantages are obtained. First, the fire hazard of working with metallic sodium is avoided. Furthermore, the metal alcoholates can be produced cheaper than the metallic sodium, and finally the working up of the higher esters of the keto acid can be accomplished easier and with smaller losses because of their lower water solubility, than that of the esters of the lower alcohols. For the further working of the keto acid esters, which mainly serve for condensations in which the alkyl radical is split off, the introduction of the alkyl radicals higher than ethyl has the further advantage that the higher alcohols can be recovered in anhydrous form with little trouble.

Eazample 1 96 parts of sodium butylate are heated with 350 parts of butylacetate and the resulting butyl alcohol in mixture with butyl acetate is distilled oft by means of a column; fresh butylacetate is added as required. The residue is acidified e. g. with acetic acid. The salt is removed and the ester mixture is fractionated preferably in vacuum. The yield of aoetoacetic acid butyl ester passing over at 16 m/m between 100 and 1025 amounts to 90% or more, calculated on the basis of the sodiumbutylate employed.

Ewample 2 110 parts of sodiumamylate are heated with 650 parts amylacetate and are treated as in Example 1. The yield of acetoacetic acid amyl esterboiling point 105-108 at 16 m/m amounts to over 80% on the basis of the sodiumamylate employed.

In the same manner butylor amylacetate can be condensed with other mono-carboxylic acid esters with the help of alcoholates. The esters of di-and poly-carboxylic acids can likewise be subjected to this condensation. In this manner oxalacetic acid butyl ester can be smoothly produced.

Claims:

1. Method of producing keto acid esters comprising reacting a carboxylic acid ester of an aliphatic alcohol having more than three carbon atoms with an alkali metal alcoholate of an aliphaticalcohol having more than three carbon atoms.

2. Method of producing keto acid esters comprising reactmg a carboxylic acid ester of an aliphatic alcohol having more than three carbon atoms, with the corresponding alkali metal alcohola'te.

3. Method of producing keto acid esters comprising reacting a mono-carboxylic acid ester of an aliphatic alcohol having more than three carbon atoms with the corresponding alkali metal alcoholate.

4:. Method of producing acetoacetic acid esters comprising reacting an acetic acid ester with sodium amylate.

Signed at Munich, this 23rd day of June,

of an aliphatic alcohol having more than three carbon atoms with an a ali metal a1- coholate of an aliphatic alcoho having more than three carbon atoms.

5. Method of producing acetoacetic acid butyl ester comprising reacting butyl acetate With sodium butylate.

6. Method of producing acetoacetic acid amyl ester comprising reacting amyl acetate DR. PAUL HALBIG. DR. FELIX KAUFLEB. DR. PET. SOHMITZ. 

